This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to 86 385/1999 filed in Japan on Mar. 29, 1999; the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a scrubbing dust collector for subjecting an exhaust gas from discharged from a semiconductor-manufacturing unit or the like to scrubbing and dust-collection, and relates to an exhaust gas treatment installation comprising this scrubbing dust collector.
2. Description of the Related Art
In the manufacture of semiconductors, an exhaust gas containing poisonous gases such as silane gas is produced. Therefore, it is obliged in accordance with a low (High pressure gas control low) to install, in a place where such an exhaust gas is discharged, an exhaust gas treatment installation, and to discharge the exhaust gas after the poisonous gases are made harmless.
As an exhaust gas treatment installation of the prior art, there has been used, for instance, one comprising a combustor for burning an exhaust gas and a jet type scrubbing dust collector for subjecting the exhaust gas burned in this combustor to scrubbing and dust-collection. In a case where a removal treatment of, for example, silane gas (SiH4) contained in an exhaust gas is carried out in such an exhaust gas treatment installation, said exhaust gas is first reacted with oxygen in air by the combustor and a combustion exhaust gas containing the resulting particles (SiO2) is mixed with cooling air so as to be cooled down to about 80xc2x0 C. By contacting the exhaust gas with a washing liquid (in general, water) by use of the scrubbing dust collector, SiO2 is thereafter caught in the washing liquid, and namely SiO2 is removed from the exhaust gas.
In the aforementioned prior art, however, there has been such a problem that it is very difficult to catch fine dust particulates whose diameter is as small as 0.1xcx9c0.5 micron, of dust particulates contained in an exhaust gas, by a circulating washing liquid so that the same fine dust particulates are permitted to be directly released to the atmosphere.
It is an object of the present invention to provide a scrubbing dust collector and an exhaust gas treatment installation capable of catching fine dust particulates in an exhaust gas by a washing liquid, thereby decreasing dust particulates released to the atmosphere.
In order to achieve the aforementioned purpose, the invention of the first aspect provides a scrubbing dust collector comprising a washing liquid tank containing a washing liquid stored therein, and a scrubbing tower provided on the upper portion of said washing liquid tank and having a washing liquid jetting means for jetting said washing liquid, where an exhaust gas is introduced into said scrubbing tower so as to be subjected to scrubbing and dust-collection, characterized in that a netting member is provided below said washing liquid jetting means in said scrubbing tower.
By virtue of the provision of the netting member, as mentioned above, a washing liquid jetted from the washing liquid jetting means collects temporarily in a section of the netting member so that a liquid membrane is formed. When the washing liquid passes through the meshes of the netting member, the same washing liquid falls down as it packs the exhaust gas, and hence the contact area of the exhaust gas containing fine dust particulates with the washing liquid becomes larger, whereby the fine dust particulates are easily caught in the washing liquid. Accordingly, the fine dust particulates removed from the exhaust gas increase, and as a result, dust particulates released to the atmosphere decrease.
In the aforementioned scrubbing dust collector, a plurality of the netting members are preferably disposed vertically. Even if fine dust particulates contained in the exhaust gas are not caught in the washing liquid in a section of the netting member on the upper side, owing to this construction, they will be caught in the washing liquid in a section of the netting member on the lower side. Namely, fine dust particulates are surely removed from the exhaust gas and dust particulates released to the atmosphere further decrease.
In this case, the mesh size of the netting member on the lower side is preferably made smaller than that of the netting member on the upper side. Owing to this construction, dust particulates of a so-called group of cluster particles formed by combining a plurality of fine dust particulates whose diameter is for example as small as 0.1 micron, of dust particulates contained in an exhaust gas, are caught by the washing Liquid in a section of the netting member on the upper side, and fine dust particulates as simple substances will be caught by the washing liquid in a section of the netting member on the lower side. Accordingly, fine dust particulates are removed from the exhaust gas, with an excellent efficiency.
Further, a frame body having slits formed therein is preferably provided below said washing liquid jetting means in said scrubbing tower, and said netting members are preferably attached below said slits in said frame body. If the quantity of the washing liquid collecting in a section of the netting members becomes larger, owing to this construction, the washing liquid will be discharged out of the frame body through said slits.
By attaching an ultrasonic vibrator on said frame body, furthermore, the clogging of the netting members can be prevented, and at the same time the fine dust particulates-collecting efficiency can be improved.
In order to achieve the aforementioned purpose, the invention of the second aspect provides an exhaust gas treatment installation comprising a combustor for burning an exhaust gas and the aforementioned scrubbing dust collector for subjecting the exhaust gas burned in this combustor to scrubbing and dust-collection. Owing to this construction, fine dust particulates removed from an exhaust gas increase and hence dust particulates released to the atmosphere decrease, as mentioned above.